Why does excessive tightening force change the initial wavelength of the sensor?
Excessive tightening force directly induces strain on the Fiber Bragg Grating (FBG) sensor. The Bragg wavelength of an FBG is determined by the effective refractive index of the fiber core and the grating period. When the sensor is subjected to strain, both the grating period and the effective refractive index of the optical fiber change due to the photoelastic effect. These changes collectively lead to a shift in the initial Bragg wavelength.
Essentially, the mechanical deformation caused by the tightening force alters the fundamental properties of the grating, resulting in a measurable wavelength shift.
OFSCN provides various types of FBG strain sensors designed for accurate measurement of such forces. For instance, the OFSCN® Alloy Tube Packaged Fiber Bragg Grating strain sensor is robust and suitable for different installation methods where forces are applied.
Here is an image of a typical FBG strain sensor:
You can find more technical details about our strain sensors here:
OFSCN® Alloy Tube Packaged Fiber Bragg Grating Strain Sensor
OFSCN® Polymer-encapsulated Fiber Bragg Grating Strain Sensor